preliminary design review. outline background information o team and motivation project focus o...

PRELIMINARY DESIGN REVIEW

Outline Background

Informationo Team and Motivation

Project Focuso Mission Statemento Design/Performance

Criteriono Goalso Inspiration

Design Overview - Primary

o Overall Concept and Generation

o Mechanism Design

Primary Analysiso Kinematicso Cam Profileso Gear Ratioo Torqueo Packagingo BOM

Controlso Hardware and Packagingo Software

Design Overview - Secondaryo Overall Concept and

Generationo Mechanism Design

Logisticso Costo Schedule

Speaker: Nick Schwartzers

2

Team and Motivation

BACKGROUND INFORMATION


3

Team Composition


4

Objective5

To design and create an automatic Continuously Variable Transmission (CVT) for a bicycle, eliminating discrete steps in gear ratio in order to maintain the ideal human cadence, with no user input.


Motivation

For years bicycles have relied on the same basic transmission design.

While this is an efficient and light weight design, there could be massive improvements for the average recreational rider

The inexperienced casual rider is often bewildered by derailleur shifting

Increase human efficiency by continuously maintaining the ideal cadence

Make bicycling more user friendly in order to elevate bicycling as viable transportation and reduce emissions


6

Human Efficiency vs. Cadence7

Cadence: The pedaling speed in RPM’s

The optimum cadence for human efficiency is shown to be near 100 rpm

This will lead to lower fatigue and a more enjoyable experience

Taken from : Cycling Science Speaker: Nick Schwartzers

Comparison to Current Designs8

0 20 40 60 80 100 120 140

Shift Points of Various Systems

Road DoubleRoad CompactMounatian TripleNexus 8Shift CVTLinear (Shift CVT)Linear (Shift CVT)

Gear Ratio (Gear Inches)

Dots Represent Shift Points

SHIFT CVT Has seamless gear free shifting

Gear Inches: the diameter of the drive wheel times the gear ratio


You’ll have an infinite number of ratios within its range to seamlessly transition to exactly the right ratio for you and your personal riding style.

Mission Statement, Goal, and Design Criteria

Project Focus


9

Mission Statement

TO PROMOTE THE ACTIVITY OF BICYCLING BY ENHANCING THE EXPERIENCE FOR THE CASUAL RIDER, BY DESIGNING, DEVELOPING, AND PROTOTYPING A DEVICE THAT WILL OPTIMIZE THE PEDALING SPEED OF THE USER THROUGH A CONTINUOUSLY VARIABLE TRANSMISSION WHILE REMAINING AESTHETICALLY PLEASING. BICYCLING WILL BECOME A MORE ENJOYABLE MEANS OF EXERCISE OR MODE OF TRANSPORTATION. WE AIM TO PROMOTE CLEANER TRANSPORTATION AND A HEALTHIER POPULATION.

“

”Speaker: Nick Schwartzers

10

Goals

Requires minimal user input and easy to use. Contains a gear range suitable for average rider. Automated and maintains user-selected, constant

cadence. Automatically adjusts gears for riders preference,

position, and conditions. Compact, unobtrusive and light-weight.

Uses a standard interface to easily mount to any bike frame.

System is safe and low maintenance. Quiet and efficient


11

Design Criteria

Maximum of 10 net pounds of additional weight Q-factor < 12 inches Efficiency of 85% Gear ratio range of at least 1:1 to 3 ½: 1 Controls cadence to within 5 rpm while bike is in

gear range Retail Price Below $300 Maintenance of 1 year or 2,000 miles No more than 20% increase in noise (decibels)


12

Inspiration and Ideas

Concept Generation


13

House of Quality

Results:

Emphasis on Packaging, contact stress, torque capability


14

Previous CVT Work

Four Different Types of CVTs have been developed:

Variable diameter pulley systems

Toroidal or roller-based CVT

Hydrostatic CVTs

Ratcheting CVTs


15

Decision Matrix16

Ratcheting Roller Based

Hydrostatic

Variable Pulley

Efficiency

Rotational Speeds

Contact Stress

Weight

Controls= Optimal= Acceptable= Unacceptable

Ratcheting CVT

Uses static friction ratchets as opposed to dynamic friction

Uses variable kinematics to change ratios.

Capacity to handle larger torques without slipping


17

Ratcheting CVT Example18


Primary Design: Non Variable Cam

DESIGN OVERVIEW19

Assembly Models


20

Assembly Models


21

Assembly Models


22

Sub Systems

Cam and input shaft Follower assembly Moving output shaft Motion Control


23

Assembly Models24


Assembly Models


25

Primary Design: Non Variable Cam

Design Analysis26

Desired Characteristics

Constant output torque Constant follower velocity vs cam angle At least 1 follower in this segment at all

positions Continuous displacement and velocity Requirements for cam:

Constant Velocity segment Smooth return Low pressure angle No undercutting

Speaker: Tom Gentry

27

Lift Curve

Speaker: Tom Gentry

28

Cam

Lift

(in)

Cam Angle (Degrees)

Lift

Follower 1 Lift

CycloidalHalf Rise Constant Velocity Rise Cycloidal

Half RiseCycloidal

Fall

Lift Curve

Speaker: Tom Gentry

29

-0.2

0

0.2

0.4

0.6

0.8

1

1.2

0 50 100 150 200 250 300 350 400

Cam

Lift

(in)

Cam Angle (Degrees)

Lift

Follower 1 Lift Follower 2 Lift

Kinematic Analysis of the Cam/Follower System

Speaker: Tom Gentry

30

Kinematic Analysis of the Cam/Follower System

Speaker: Tom Gentry

31

Design Inputs

Variable Value Unit Data type RangeSmooth Lift (in) 0.11 inches real 0,1

Chain ring (tooth) 106 tooth integer 11,106Input Gear (tooth) 11 tooth integer 11,53

Cam Rises 2 integer integer 1,10Followers 2 integer integer 2,2

Base circle diameter (in) 3.5 inches real 0,5Planet Shaft to Cam Clearance (in) 0.1 inches real 0,3

Output Gear (tooth) 30 tooth integer 11,53Back wheel Gear (tooth) 11 tooth integer 11,53

Quick Return 3.7 ratio real 1.01,10Eccentricity (in) 0 inches real -1,1

Roller Diameter (in) 0.5 inches real .25,1.5Output Shaft Travel (in) 6 inches real 0,15

Preload (lbf) 8 lbf real 0,200Follower Type Roller N/A N/A Roller

Rise Constant V N/A N/A Constant VFall 1 Cycloidal/SHM integer 1,2

alpha (rad/s^2) 0 rad/s^2 real -100,100Single/Variable Profile Single N/A N/A Single

Input Shaft Torque (ft-lb) 114.8293963 ft-lb real 0,120Follower Mass 0.2 lbm real 0,200Cadence (rpm) 110 rpm real 0,150

Speaker: Tom Gentry

32

Kinematics

0 50 100 150 200 250 300 350 400

-4

-3

-2

-1

0

1

2

3

4

5

0

0.2

0.4

0.6

0.8

1

1.2

Velocity

Follower 1 Velocity Follower 2 Velocity Follower 1 Lift Follower 2 Lift

Cam Angle (Degrees)

Follo

wer

Vel

ocity

(ft/s

)

Lift (i

n)

Speaker: Tom Gentry

33

Kinematics

0 50 100 150 200 250 300 350 400

-2000

-1500

-1000

-500

0

500

1000

1500

2000

0

0.2

0.4

0.6

0.8

1

1.2

Acceleration

Acceleration Follower 1 Acceleration Follower 2 Lift Follower 1

Cam Angle (Degrees)

Follo

wer

Acc

eler

ation

(ft/s

^2)

Lift (i

n)

Speaker: Tom Gentry

34

Kinematics

0 50 100 150 200 250 300 350 4000

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0.5

Follower Angle

Follower 1 high gear Follower 1 low gear Follower 2 low gear Follower 2 High gear

Cam Angle (deg)

Angle

(ra

d)

Speaker: Tom Gentry

36

Cam Profile

-3 -2 -1 0 1 2 3

-3

-2

-1

0

1

2

3

Cam Profile

Pitch Curve Base Circle Cam Surface Roller

X ( in)

Y (

in)

Speaker: Tom Gentry

37

Output Analysis

0 50 100 150 200 250 300 350 4000

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

0

0.2

0.4

0.6

0.8

1

1.2

Output Velocity

Equivalent Follower Output Velocity Lift Follower 1

Cam Angle (Degrees)

Out

put F

ollo

wer

Vel

ocity

(ft/s

)

Lift (i

n)

Speaker: Tom Gentry

38

Output Analysis

0 50 100 150 200 250 300 350 4000

20

40

60

80

100

120

140

160

180

Clutch Torque

High Gear Low Gear

Cam Angle (Degrees)

Torq

ue (ft

-lbf)

Speaker: Tom Gentry

39

Output Analysis

0 50 100 150 200 250 300 350 400

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

Inertial Force on Cam

Follower 1 Follower 2

Cam Angle (deg.)

Forc

e (

lbf)

Speaker: Tom Gentry

40

Design OutputsVariable Value Unit

Total Lift (in) 0.985925926 inchesMinimum Case Height 11.0726239 inches

w 111.0029404 rad/sOutput Travel per rise (high) (deg) 0.466063428 degOutput Travel per rise (low) (deg) 0.140719761 deg

Final ratio (high) 4.678624042 ratioFinal ratio (low) 1.412629302 ratio

Total Ratio 3.311997023 ratioMax Lead Screw Force (lbs) 36.37085325 lbs

Speed (mph) (low) 12.08386649 mphSpeed (mph) (high) 40.02172982 mph

Gearbox Input Torque (Low) (ft-lb) 11.91625811 ft-lbOutput Gear Torque (Low) (ft-lb) 170.0913578 ft-lb

Rear Wheel (Low) (ft-lb) 103.9447186 ft-lbGearbox Input Speed (low) (rpm) 110 rpmOutput Gear Speed (low) (rpm) 1060 rpmRear Wheel Speed (low) (rpm) 94.96008084 rpm

Gearbox Input Torque (high) (ft-lb) 11.91625811 ft-lbOutput Gear Torque (high) (ft-lb) 47.89929041 ft-lbRear Wheel Torque (high) (ft-lb) 29.27178858 ft-lb

Gearbox Input Speed (high) (rpm) 110 rpmOutput Gear Speed (high) (rpm) 1060 rpmRear Wheel Speed (high) (rpm) 314.507505 rpm

Minimum Spring Constant (lbf/in) 2.893935408 lbf/inConcave Profile? 1 boolean

Maximum Pressure Angle (deg) 1.504222056 degAllowable Radius of Curvature? (roller) 1 boolean

Minimum Concave Radius of Curvature (in) 9999 inSpring Force % 3.843095842 %

Spring Compression (in) 3.750327639 in

Speaker: Tom Gentry

41

Efficiency

Major Contributions: Kinematics ~94% (High), ~99.8% (low) 2 Chains ~98% each Follower Sliding Friction ~7.5% (High),

~1.8% (Low) Roller Follower Rolling Resistance ~3.2% Spring Energy ~3.2%

High Gear Efficiency – 80% Low Gear Efficiency – 86%

Speaker: Tom Gentry

42

Losses

Speaker: Tom Gentry

43

0.00%

1.00%

2.00%

3.00%

4.00%

5.00%

6.00%

7.00%

8.00%

9.00%

0 50 100 150 200 250 300 350 400

Loss

%

Cam Angle

Major Losses

Chain Losses Spring Losses Cam Pressure Angle Losses Follower Pressure Angle Losses Friction and Rolling Resistance Losses

- Friction and Rolling

- Chain

- Spring

- Cam Pressure Angle- Follower Pressure Angle

Due To:

Efficiency

Speaker: Tom Gentry

44

0 50 100 150 200 250 300 350 4000.00%

10.00%

20.00%

30.00%

40.00%

50.00%

60.00%

70.00%

80.00%

90.00%

100.00%

Total Efficiency

High GearLow Gear

Cam Angle

Syste

m E

fficie

ncy

Design Optimization

Parametric Model Optimization method

Gradient based Non gradient based

Inputs Ranges/types

Outputs Maximize/Minimize/Target

Speaker: Tom Gentry

45

Excel Parametric System Model

Speaker: Tom Gentry

46

Isight Capabilities47

Speaker: Tom Gentry

Isight Capabilities

http://www.simulia.com/download/products/Fiper_Isight35_web.pdf

Speaker: Tom Gentry

48

Gear Ratio

Speaker: Andrew Shaw

High Gear (3.5:1) Low Gear (1:1)

49

Output Analysis – Gear Ratios and Torques

Gear Ratios: High Gear Low Gear UnitStart angle 0.0 0.0 radEnd Angle 0.5 0.1 rad

Output Travel per rise 0.5 0.1 radOutput Travel per rise 26.7 8.1 deg

Output Travel per crank 1029.3 310.8 degBack wheel per crank 1684.3 508.5 deg

Final ratio 4.7 1.4 :1Total Ratio 3.3

Shaft Torque (low Gear) (ft-lb)Input Shaft 114.8293963

Gearbox Input 11.9Output Gear 170.1Rear Wheel 103.9

50


Follower Type

Pros: Flexibility with cam

profile (positive radius of curvature)

Multiple rises Less wear

Cons: More Parts Slightly more contact

stress

Pros: Lower number of

parts Pressure angle is

always 0 Cons:

Wear Friction Losses Spring Packaging

Translating Roller Follower

Oscillating Flat Faced Follower


51

Roller Follower Selection

Max Allowable stress of 100 kpsi given by manufacturer

Stud Bending Stress

Cam Contact Stress

Follower Bearing Fatigue


52

Contact Stress

Max Contact Pressure

Principle Stresses


53

Contact Stress cont.


σx= -34922.175525717 PSIσy= -23696.480153326 PSIσz= -96310.995880065 PSI

taumax= 36307.257863370 PSI

Cam Roller

AISI 4140 AISI 52100

Processing Quenched & Tempered @ 425°C

Quenched & Tempered

Tensile Strength(kpsi) 181 325

Yield Strength(kpsi) 165 295

Brinell Hardness 370 518

Factor of Safety 1.87 3.73

Normally contact strength is a factor of 2 more than Sut

54

Contact Stress cont.

To reduce the contact force: Change the transmission kinematic parameters

Increase cam rotation speed Increase amount of rise Increase number of cam rises

To reduce contact stress: Reduce the contact force Increase the diameters of the contacting bodies Reduce the modulus of elasticity of the materials

involved Change the geometry of the contact region


55

Contact Fatigue

1000 1200 1400 1600 1800 20000.4

0.6

0.8

1

1.2

1.4

1.6Factor of Safety The-

oretical

Factor of Safety

Hours

Facto

r of

Safe

ty

•This is with an experimental K = 9000 for 4150 steel. Our calculated K needed is 108.

•Take away is we can use a weaker material but for yielding we are using a harder material, which gives an infinite life for contact fatigue.

1000 1500 20000

5E+016

1E+017

1.5E+017

Factor of Safety Needed K

Factor of Safety

Hours

Facto

r of

Safe

ty56


Follower Arm Stress

,a f a nomK

,m f m nomK

11

1

tf

KK

ar

0.5e utS S

ba utk aS

1

/ /fa e m ut

nS S

( )

yy

a M

Sn

e a b c d e f eS k k k k k k S

Critical plane at the end near fillet.


Factor of safety=2.55

57

Spring Force

A spring is used to keep the follower in contact with cam and must be capable of applying a force equal to inertia force.

F - mfg - S(X - xo) = mf Af

F = contact force, mf = mass of the follower, Af = acceleration of the follower.

Neglect gravity


Spring Constant Preload 8 lbfFollower Mass 0.00621118 slug

Minimum Spring Constant 2.893935408 lbf/inMinimum Net Force 282.4 lbf

Spring Force/min net force % 3.8Spring Compression 3.8 in

0 50 100 150 200 250 300 350 400

-0.4

-0.2

0

0.2

0.4



Cam Angle (deg.)

Forc

e (

lbf)

58

Sprag Clutch

Selected based on torque, speed and axial load

Transmits high torque compared to other devices

Similar to a bearing but allows only one way rotation


59

Bearing Selection

60 D DL L n rpmDn hrsDL

10D

Lx

L

10L RatingLife

1/

10 1/0 0( )(1 )

a

DD b

D

xC F

x x R

0.9DR 0 , , and x b Wiebull Parameters 3a

•No Axial Load•Sealed single row deep groove ball bearings•Bearings are available in suitable sizes for this project


60

Material Selection

Cam RollerAISI 4140 AISI 52100

Processing Quenched & Tempered @ 425°C

Quenched & Tempered

Tensile Strength(kpsi) 181 325

Yield Strength(kpsi) 165 295

Brinell Hardness 370 518

Endurance Limit Strength (kpsi)

90.5 100

Modulus of Elasticity(106 psi)

29.2 29.5

Poisson’s Ratio .29 .3

Machinability .65 .40Speaker: Andrew Shaw

61

Packaging

Mounts to existing bike frame with clamps

Provides adequate clearances Aluminum case Chain tensioner Translucent side to see operation Low center of gravityFollower length 8.3 inches

Minimum Case Height 5.6 inchesIncluding Followers 11.1 inches


62

BOM

CONCEPT 1 BOM

ITEM COMPANY PART # QUANTITY Price Line Cost

RBC Follower Bearing Engineering S16LWRBC 2 $13.80 $27.60 Rail Guide Grainger 2CRR8 2 $19.25 $38.50 Carriage Grainger 2RLE4 2 $27.80 $55.60

Sprag Clutch VXB Kit8182 2 $19.95 $39.90 Shaft 8x1/2 McMaster-Carr 6061K103 2 $4.33 $8.66

Bearing McMaster-Carr 6384K49 4 $8.33 $33.32 Sprocket McMaster-Carr 6280K661 2 $11.05 $22.10

Chain Price Point 25068 2 $12.98 $25.96 Aluminum for Housing Metal Depot S318 1 $37.40 $37.40

Follower Arms AL 6061 1'x1.5"x.5" McMaster-Carr 6023K251 1 $15.92 $15.92

Springs McMaster-Carr 9657K128 (12ct.) 1 $6.97 $6.97

Retainer Clips for 1/2" Shaft McMaster-Carr 9590A122 (10ct.) 1 $8.94 $8.94

Aluminum Carriage 5"x2"x2" Metal Depot SQ32 1 $26.94 $26.94 Woodruff Key Home Depot 79758 2 $0.25 $0.50

4140 Steel for Cam McMaster-Carr 8960K61 2 $23.96 $47.92 Miscellaneous 1 $100.00 $100.00

Total = $496.23 Speaker: Andrew Shaw

63

Control System-Concept Selection-Functional Diagrams-Equipment Selection

64

System Control Concept Selection

Mechanical Electro-Mechanical

Electrical

Weight High Medium Medium

Output Force Very Low High High

Adjustability Very Low Medium Very High

Accuracy High Low Very High

Cost Medium Low High

Power Source Rider Battery Battery

Position Control Difficulty

Medium High Very Low

Speaker: Brian Pigman

65

Functional Diagram

Wheel Speed

Optimal Cadence

Desired Gear Ratio/Position

Gear Position

PLC Controller

Drive and Motor

Encoder

Power Source


66

Electrical Control Components

- Optical Encoder- Transduces wheel speed to pulse

- PLC- Produces output voltage based on programmed input signal conditions

- Motor Drive- Delivers power to motor- Motor- Provides output position- Lead Screw- Converts Rotary Positioning

to Linear


67

Motor Selection

Stepper Servo

Holding Torque X

Price X

Encoder Required X

Continuous X

Accuracy X X


68

Lead Screw Force

http://www.smallmotors.com/html/lead_screws.html

Fcam

Fx

Fy

Tout

Ѳ*sin( )x camF F

0xF

The follower arm and output shaft are supported by a track. There are no moments and Fx is the only force on the lead screw


69

http://www.smallmotors.com/html/lead_screws.html

Lead Screw Force


0

0.2

0.4

0.6

0.8

1

1.2

0

5

10

15

20

25

30

35

40

0 50 100 150 200 250 300 350 400

Forc

e (lb

f)

Cam Angle (deg)

Lead Screw Force

Lead Screw Force

Lift Follower 1

Lift Follower 2

70

Motor Torque

η- Efficiency P- screw pitch (revolutions/inch) F- axial load on lead screw T – required motor torque


71

Motor Torque

Typical lead screw efficiency – around .4 Screw Pitch – 10rev/1in Axial Load – 50lb

Gives a required T = 20.7 oz-in


72

Maximum Torque RPM

Assume Maximum acceleration or deceleration will

occur when braking from full speed (~35mph) to zero

Braking within 6 seconds Neglect inertia of motor and shaft

At Maximum, carriage needs to travel 6” in 6 seconds


73

Maximum Torque RPM

6 in/6sec = 1 in/sec 1 in/sec * (10 rev/in) = 10 rev/sec Maximum Torque of 20.7oz-in needed at

10rps

At the given parameters the motor produces around 42 oz-in of torque

24Vdc at 10rps


74

http://www.omega.com/Auto/pdf/2035.pdf

http://www.omega.com/Auto/pdf/2035.pdf

Hardware

Motor – Stepper Motor OMHT17-275 Drive – 2035 Programmable Logic Controller - ELC-

PB14NNDR Encoder - RB-Cyt-39

http://www.hurst-motors.com/hybridstepper.html http://www.omega.com/pptst/2035.html

http://www.omega.com/pptst/ELC_PLC.html

http://www.robotshop.com/cytron-simple-rotary-encoder-kit.html Speaker: Ernie Stoops

75

http://www.hurst-motors.com/hybridstepper.html

http://www.omega.com/pptst/2035.html

http://www.omega.com/pptst/2035.html



http://www.robotshop.com/cytron-simple-rotary-encoder-kit.html

http://www.robotshop.com/cytron-simple-rotary-encoder-kit.html

Lead Screw Buckling Analysis

F – Force to cause buckling

E – Modulus of Elasticity

I – Area Moment of Inertia

K – End Conditions

0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10

100002000030000400005000060000700008000090000

100000

Buckling Force vs. Diameter

F

Diameter (in)Forc

e (

lb)

At .5”, 5,800 lbf is needed to buckle

Max force is just over 40 lbf

Speaker: Ernie Stoops

76

Power & Weight

24 V System Running 56 W Battery is 5 A-h

Gives a battery life of just over 1.7 hours

Weight of major componentsObject Weight (lbs)

PLC 0.348Battery 4Motor 0.79

Motor Drive 0.56255.7005 TOTAL


77

Controls BOM

ITEM COMPANY PART # QUANTITY PRICEStepper Motor Omega OMHT17-275 1 $49.50

Motor Drive Omega 2035 1 $170.10 PLC Omega ELC-PB14NNDR 1 $181.80

Rotary Encoder Cytron Technologies RB-Cyt-39 1 $11.29 24 V Rechargeable Battery All-Battery 11809 1 $99.99

Battery Charger All-Battery 1007 1 $12.87 DIN Rail McMaster-Carr 8961K13 1 $4.74

Lead Screw McMaster-Carr 93255A431 1 $8.96 Platform Nut Fine Line Automation GRP108-00 1 $16.50 PLC Software Omega ELCSOFT 1 $247.50 PLC-PC Cable Omega ELC-CBPCELC1 1 $38.70

Coupler Servo City CSC-.250-.375 1 $12.99 Thrust Bearing McMaster-Carr 5909K31 1 $2.76

Total = $857.70


78

Secondary Design: Variable Cam

DESIGN OVERVIEW79

Assembly Models


80

Assembly Models


81

Assembly Models – Low Gear82


Assembly Models – High Gear83


Assembly Models


84

Assembly Models


85

Cam Profile

Produce single profile and shrink down by factor

Speaker: Tom Gentry

86

Secondary Design: Variable Cam

Design Analysis87

Cam Profile

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

2.5

-2.5 -2 -1.5 -1 -0.5 0 0.5 1 1.5 2 2.5

v (i

n)

u ( in)

Cam Profile


-3

-2

-1

0

1

2

3

-3 -2 -1 0 1 2 3

v (i

n)

u ( in)

Cam Profile


Low Gear High Gear

Speaker: Tom Gentry

88

Kinematics

-0.02

0

0.02

0.04

0.06

0.08

0.1

0.12

0 50 100 150 200 250 300 350 400

Angl

e (r

ad)

Cam Angle (deg)

Follower Angle

Follower 1 high gear Follower 2 High gear

-0.05

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0 50 100 150 200 250 300 350 400

Angl

e (r

ad)

Cam Angle (deg)

Follower Angle

Follower 1 high gear Follower 2 High gear

Low Gear High Gear

Speaker: Tom Gentry

89

Output Analysis

0

50

100

150

200

250

300

0 50 100 150 200 250 300 350 400

Torq

ue (ft

-lbf)

Cam Angle (Degrees)

Clutch Torque

High Gear Low Gear

0

50

100

150

200

250

300

0 50 100 150 200 250 300 350 400

Torq

ue (ft

-lbf)

Cam Angle (Degrees)

Clutch Torque

High Gear Low Gear

Low Gear High Gear

Speaker: Tom Gentry

90

Output Analysis

-0.1

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.1

0 50 100 150 200 250 300 350 400Forc

e (lb

f)

Cam Angle (deg.)



-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0 50 100 150 200 250 300 350 400Forc

e (lb

f)

Cam Angle (deg.)



Low Gear High Gear

Speaker: Tom Gentry

91

Output Analysis – Spring Rate

Preload 8 lbfFollower Mass 0.00621118 slug

Minimum Spring Constant 3.750161675 lbf/inMinimum Net Force 270.9 lbf

Spring Force/min net force % 4.3Spring Compression 3.1 in

8 lbf0.00621118 slug

0 lbf/in1263.4 lbf

0.60.0 in

Low GearHigh Gear

Speaker: Tom Gentry

92

Output Analysis – Gear Ratios

Gear Ratios: High GearStart angle 0.0End Angle 0.3

Output Travel per rise 0.3Output Travel per rise 19.2

Output Travel per crank 766.8Back wheel per crank 1254.8

Final ratio 3.5

Low Gear Unit0.0 rad0.1 rad0.1 rad6.0 deg

241.8 deg395.6 deg

1.1 :1

Speaker: Tom Gentry

93

Output Analysis – Torques

Shaft Torque (low Gear) (ft-lb)Input Shaft 114.8293963

Gearbox Input 11.5Output Gear 66.8Rear Wheel 40.8

Torque (High Gear) (ft-lb)114.8293963

11.566.840.8

Torque (low Gear) (ft-lb)114.8293963

11.5219.3134.0

Speaker: Tom Gentry

94

BOM

CONCEPT 2 BOMITEM COMPANY PART # QUANTITY Price Line Cost

RBC Follower Bearing Engineering S16LWRBC 2 $13.80 $27.60

Cam McMaster-Carr 9034K69 1 $149.04 $149.04 Bevel Gear Set Grainger 3ZP64 1 $115.15 $115.15 Lead Screw Nut McMaster-Carr 6350K42 1 $23.58 $23.58

Sprag Clutch VXB Kit8182 2 $19.95 $39.90 Shaft 8x1/2 McMaster-Carr 6061K103 2 $4.33 $8.66

Ball Spline Shaft Gridline Industrial SSP6S150mm 1 $102.58 $102.58 Ball Spline Nut Grainger 3HVC3 1 $101.00 $101.00

Bearing McMaster-Carr 6384K49 6 $8.33 $49.98 Sprocket McMaster-Carr 6280K661 2 $11.05 $22.10

Chain Price Point 25068 2 $12.98 $25.96 Aluminum for Housing Metal Depot S318 1 $37.40 $37.40

Follower Arms AL 6061 1'x1.5"x.5" McMaster-Carr 6023K251 1 $15.92 $15.92 Springs McMaster-Carr 9657K128 (12ct.) 1 $6.97 $6.97

Retainer Clips for 1/2" Shaft McMaster-Carr 9590A122 (10ct.) 1 $8.94 $8.94 32 Tooth Spur Gear McMaster-Carr 6325K85 3 $23.98 $71.94 65 Tooth Spur Gear McMaster-Carr 6325K73 1 $37.14 $37.14 Aluminum 2"x1"x1" McMaster-Carr 9008K141 1 $10.41 $10.41 Aluminum 3"x5"x1" McMaster-Carr 8975K313 1 $23.16 $23.16 Aluminum 1'x2"x2" Metal Depot SQ32 1 $26.94 $26.94

Woodruff Key Home Depot 79758 2 $0.25 $0.50 Miscellaneous 1 $100.00 $100.00

Total = $1,004.87


95

Final Results

Design Comparison96

Comparison of Concepts

Pros: -Easier to Machine-More efficient-Lighter weight-Cheaper ($1360)Cons:-Moving output shaft

Pros:-Possible neutral gear-Multiple input and

output configurationsCons:-More Shift Force-Heavier-Larger Package-Cost ($1870)

Non- Variable Cam Variable Cam


97

Schedule

Legend

SHIFT GANTT CHART On Time ScheduledA Approval

Task Week 1 Week 2 Week 3 Week 4 Week 5 Week 6 Week 7 Week 8 Week 9 Week 10 Week 11 Week 12 Week 13 Week 14

Organization Team Name A Team Logo A

Mission Statement A Goals A

Concept Design Design Criteria A

Concept Sketches A Preliminary Design Review

Critical Design Review Fabrication

Assembly & Integration Testing

Delivery


98

Risk

Gearbox Time Machining Packaging

Control System Time New

Programming Language

Electrical failure


99

Conclusion

SHIFT’s CVT will provide fully automatic, continuously variable gearing system that will improve experience for all riders

Team SHIFT has skills, dedication and drive to complete the development of the Bicycle CVT in allotted time

Request approval to continue with design process and begin Prototyping and preparing for Critical Design Review


100

Acknowledgements

Professor StarkeyProfessor PennockProfessor SadeghiMike Moya

101


Questions?

102

Problems encountered

Variable diameter pulley:

Low Efficiency Requires High Rotational

Speeds Hard to Control Unable to Shift while

Stationary

Hydrostatic: Heavy

Inefficient

http://cmgonline.com/content/view/2489/57/

http://auto.howstuffworks.com/cvt4.htm


103

Problems encountered cont.

Toroidal: High Contact Stress Requires Traction Fluid Tight Tolerances

required Balance of

Friction(wear), Normal Force(contact stress), Radius(size), and Angular Velocity(losses)

P T

P Fr

P Nr

http://www.nsk.com/products/automotive/drive/hcvt/


104

preliminary design review. outline background information o team and motivation project focus o...

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